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Coleman says he will step down when his current contract expires at the end of the 2018 World Cup campaign.
He guided Wales to the Euro 2016 semi-finals in their first appearance at a major tournament in 58 years.
"Hopefully we'll be able to persuade him to stay on because what we've done over the past few years has been sensational," Roberts said.
"I haven't spoken to him about it yet. The plan is to get to Russia. I'm hoping there's 12 months until that decision has to be acted upon.
"During that time I'll certainly be talking to him about it. I know how much he's enjoyed the experience leading this group of players, leading the team behind the team, and leading the nation.
"He's obviously done a remarkable job. Anything's possible in football. Things change very quickly. Hopefully on this occasion Chris will change his mind."
Coleman's side drew 1-1 away to Serbia in their recent World Cup qualifier to remain unbeaten in their group.
Wales are currently four points behind Serbia and the Republic of Ireland in group D, with four matches remaining.
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Only the winners of the nine European World Cup qualifying groups will advance automatically to next year's finals in Russia, while the eight best runners-up enter the play-offs.
However, Roberts still believes finishing top is a realistic aim and is not ready to concede that Wales cannot win the group.
"All we can do is focus on the games coming up in September. Win those and see where it takes us," he said.
"But we know that we have to take maximum points really, and that's well within the reach of this group of players.
"The aim is to finish top of the group. If that doesn't happen we'll have to aim for the play-off spot. But we're prepared for either [scenario]."
After beating Moldova in their opening game in the group, Wales have drawn their last five matches.
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But Roberts says the coaching team have been happy with the performances.
"We've created more chances than the opposition in each of those games. So it's fine lines," he said.
"When we look at the games against Serbia - in the home game, they had one effort on target and they scored. And yet again last week they get one effort on target and they score.
"It's very difficult to stop a team for 90 minutes from getting one effort on target.
"Based on statistics, we've been really unlucky not to get maximum points out of most of the games, apart from [the 1-1 draw] with Georgia. That's the only game we didn't deserve maximum points.
"But we are where we are. We've got to continue to work hard. And we've got to continue to be effective in that final third, in particular in open play."
Wales assistant boss Osian Roberts hopes Chris Coleman can be persuaded to extend his stay as Wales manager.

John Sullivan, 66, of Abergavenny, was pulled from the River Usk, near the town's Llanfoist Bridge, on Monday morning, but was pronounced dead at the scene.
Fire crews from Abergavenny and Blaenavon were involved in the search.
Inquiries are ongoing to establish the circumstances surrounding his death.
A man who died after being rescued from a river in Monmouthshire has been named.

He replaces Andrew Bailey, who earlier this year was made the permanent boss of sister watchdog the Financial Conduct Authority (FCA), the City watchdog and the UK's most prominent financial consumer protection body.
Mr Woods currently oversees insurance supervision at the PRA.
He will start in his new job in July.
The PRA oversees the work of 1,700 banks, building societies, credit unions, insurers and major investment firms.
Mr Woods spent 10 years at the Treasury before he joined the Bank of England, where he had a variety of roles, including secretary of the Independent Commission on Banking. Before that, he worked in the private sector from 1995-2001, for drinks giant Diageo and consultants McKinsey.
The Chancellor, George Osborne, said: "Sam has been one of the architects of the government's crucial reforms to financial regulation - playing a key role in the work of the Independent Commission on Banking.
"I believe Sam is the best person to ensure that these vital reforms he helped design will be a success and to deliver a strong, secure and globally competitive regime for all financial services."
Mr Bailey, who was unable to start his new job at the FCA until a replacement was found, himself replaces Martin Wheatley, who left the organisation last September.
Tracey McDermott has been in charge of the FCA on an interim basis, but ruled herself out of the permanent job in January.

Sam Woods has been appointed as a Bank of England deputy governor and head of the Prudential Regulatory Authority, which oversees the banking sector.

